On p. 2759 Lane Baker and co-workers from Indiana University and Oak Ridge National Laboratory describe electromagnetic micropores for the control of ion transport. Current passed through a single-turn microcoil focuses a magnetic field gradient, creating a trap at a micropore in the center of the coil. Magnetic fluids trapped in the electromagnetic trap can be used to gate the flux of ions through the micropore, in a manner reminiscent of biological ion channels. Further applications in nano-/microscale transport and sensor development are evident.

A directed self-assembly approach to fabricate multiple-particle arrays on template surfaces is presented. The colored SEM image shows deposited 200, 350, and 500 nm polystyrene particles, which are sequentially assembled from aqueous suspensions at size-selective assembly sites in work reported by Heiko Wolf and co-workers on p. 2804. Particle size dependent capillary and confinement forces that act at the menisci of the suspensions were harnessed to afford selectivity. Once selectively assembled, the particles were transferred in a one-step printing process.

Article first published online: 14 MAY 2010 | DOI: 10.1002/adma.201000260

Multifunctional magnetic nanoparticles (MFMNPs) have been demonstrated to have great promise as multimodality imaging probes. Here, after a quick reminder of the various ways of synthesizing magnetic NPs, we review recent progress in the design, synthesis, functionalization, and biomedical applications – such as molecular imaging and the targeted delivery of biomedicine, for example to treat cancer – of MFMNPs.

Highly conductive semitransparent graphene sheets are combined with an n-type silicon (n-Si) wafer to fabricate solar cells with power conversion efficiencies up to 1.5% at AM 1.5 and an illumination intensity of 100 mW cm−2. The Schottky junction solar cells can be extended to other semiconducting materials in which graphene serves multiple functions as active junction layer, charge transport path, and transparent electrode.

Highly stretchable and robust antennas are fabricated by injecting liquid metal into a microfluidic channel that consists of two types of silicone rubber with different stiffness. The resulting antennas exhibit high mechanical stability under strain, while retaining high stretchability; these antennas can be stretched by up to a tensile strain of 120 % with little degradation in radiation efficiency.

Doped photoresponsive nanodevices. A thiol end-capped and iodine-doped sexithiophene disulfide polymer is used to bridge nanogap gold electrodes via an in-situ oxidation, doping, and self-assembly method. Temperature-dependent semiconducting and photoresponsive nanodevices are formed and Coulomb-blockade phenomena are observed in these organic molecule-based nanodevices.

Gating of a single pore with a microelectromagnetic trap consisting of a single-turn gold wire microfabricated on a silicon membrane is described. A single micrometer-sized pore in the center of the microcoil conducts ionic current under the application of an applied transmembrane potential. When energized, the microelectromagnetic trap attracts a droplet of magnetic fluid, bringing the fluid to rest in the center of the trap, blocking the transport of ions through the pore, turning it “off”. Reversal of the current flow through the trap moves the droplet to the periphery of the trap, turning the pore “on”.

Tunable multicolor organic patterns based on two dye molecules are demonstrated. The left-hand fluorescence microscopy image shows the emission for 32 nm DtCDQA on narrow Au lines and 1 nm on the SiO2 substrate. Subsequent deposition of the second dye, NPB, can create tunable multicolor patterns by controlling the emission from NPB and the monomer and aggregates of DtCDQA. Depositing 10 nm NPB gives orange on green (upper right), and 100 nm NPB, green on blue (lower right).

A bulk metallic glass (BMG) composite with large tensile ductility and work-hardening capability (see figure) was developed by applying the “transformation-induced plasticity” concept to amorphous alloys. The current approach is not believed to be limited to the current BMG composite but could promote ductility in other BMG systems, offering a new paradigm for developing BMGs with improved ductility as practical engineering materials.

Co-assembly of cadmium selenide nanorods in block copolymer films gives rise to anisotropic, hierarchical nanorod superstructures at the film surface. Unlike their observed behavior in the bulk composite, the nanorods preferentially orient perpendicular to the direction of the block copolymer domain, and the number of nanorods assembled across the domain is controlled by the ratio between the nanorod length and the domain width.

Several porphyrin-dimer tapelike molecule/C60 heterojunction detectors are investigated. Their extended π-electron systems provide photovoltaic response into the near infrared, with an external quantum efficiency of up to 6.5% at a wavelength of λ = 1350 nm. Additionally, a specific detectivity of D* = 1.6 × 1011 Jones at λ = 1090 nm, and (2.3 ± 0.1) × 1010 Jones at λ = 1350 nm are detected. The optical response time of the detectors is resistance–capacitance limited at 1.87 ± 0.03 ns.

A thermally reversible polymeric network with imbedded ferromagnetic particles was synthesized via the Diels-Alder reaction. When placed in an alternating magnetic field (see figure) the material is heated in situ by the self-limiting heating behavior of ferromagnetic particles and subsequently reverts to a liquid. As a consequence, the material properties are unchanged even after ten cycles of fracture and repair.

A fully reversible polymeric color-switch system based on reversible Diels-Alder chemistry between cyclopentadienyl capped polymers and highly electron deficient dithioesters is described. The detailed reaction progress could be mapped on a molecular level for several complete switching cycles and was underpinned by an ESI-MS study.

A novel multifunctional, proton-fueled DNA nano-spring has been constructed. By incorporation of the G-quadruplex/i-motif sequence into the assembly, the nanodevice can perform spring-like motions in response to changes in the environmental pH without permanent deformation. Nanosized objects/functional groups could be assembled/disassembled into this system in an addressable, contractile, and reversible manner.

Bulk electron transport in a high mobility n-type polymer is studied by time-of-flight photocurrent measurements and electron-only devices. Bulk electron mobilities of ∼ 5×10−3 cm2/Vs are obtained. The analysis of the electron currents suggests the presence of an injection barrier for all conventionally used low workfunction cathodes.

A novel and versatile processing method is developed for the formation of nanoporous scaffolds with in-situ enzyme immobilization for highly sensitive biosensor applications. The nanoporous scaffold-based biosensor shows high sensitivity, stability, selectivity, and good precision. This flow-induced immobilziation technique opens up new pathways for designing simple, fast, biocompatible, and cost-effective processes for enhanced sensor performance.

A gold marker technique that allows to measure wear with nanometer resolution laterally and normal to a materials surface has been developed. By way of analysis of gold concentration profiles before and after rubbing, the method can distinguish newly added from original material and afford information on phase-specific wear and sub-surface processes that occur in aluminium-silicon alloys.

Nanoelectronic biosensing using field-effect transistors fabricated by nanostructured materials promises novel applications in detecting dynamic activities of living cells. We report on the recent developments on this emerging technique.